US 20080175586 A1
Embodiments of the present invention compensate for skew across a wavelength division multiplexed network. The network is a wavelength division multiplexed optical transport network. The skew compensation can be performed electrically or optically. It can be performed on the transmission side of the network, the receiver side of the network or at any intermediary node on the network.
1. A networking system for routing a signal, the system comprising:
a transmission node that transmits the signal;
a first path that transports a first portion of the signal;
a second path that transports a second portion of the signal;
a skew compensation module, coupled within the networking system, that compensates for skew relative to the first and second paths whereby the resulting skew relative to the first and second paths is within a skew limit; and
a receiver node that receives the first and second portions of the signal.
2. The networking system of
3. The networking system of
4. The networking system of
5. The networking system of
6. The networking system of
7. The networking system of
8. The networking system of
9. The networking system of
10. The networking system of
11. The networking system of
12. A transceiver that compensates for skew, the transceiver comprising:
an input on which a signal is received;
a deinterleaver, coupled to the input, that partitions the signal into a first signal portion that can be transmitted on a first communication path and a second signal portion that can be transmitted on a second communication path; and
a skew compensation module, coupled to the deinterleaver, that compensates for skew relative to the first and second communication path.
13. The transceiver of
14. The transceiver of
15. The transceiver of
16. A transceiver that compensates for skew, the transceiver comprising:
a first input on which a first input portion is received;
a second input on which a second input portion is received;
a skew compensation module, coupled within the transceiver node, that compensates for skew relative to the first and second signal portions;
a first output on which a first output portion is transmitted;
a second output on which a second output portion is transmitted.
17. The transceiver of
18. The transceiver of
19. The transceiver of
20. A method for compensating for skew, the method comprising:
providing a first communication path for transmitting a first portion of a signal;
providing a second communication path for transmitting a second portion of the signal; and
compensating for skew relative to the first and second communication paths such the relative skew is equalized.
21. The method of
22. The method of
23. The method of
24. The method of
25. The method of
26. The method of
This application is related to U.S. Provisional Application Ser. No. 60/885,832, entitled “Communication Network with Skew Path Factoring,” filed Jan. 19, 2007; U.S. application Ser. No. 11/781,912, filed on Jul. 23, 2007 entitled “Communication Network With Skew Path Monitoring and Adjustment;” and U.S. application Ser. No. 11/856,692, filed on Sep. 17, 2007, entitled “Communication Network With Skew Determination;” all of which are incorporated herein by reference in their entirety.
A. Technical Field
This invention relates generally to optical transport networks, and more particularly to the management of skew across a wave division multiplexed network.
B. Background of the Invention
Optical networks are able to communicate information at high data rates. An optical transport system 10 is shown in
Embodiments of the present invention compensate for skew between multiple paths in an optical network. The network can be a wave division multiplexed (“WDM”) optical transport network using wavelength division multiplexed wavelengths and/or optical carrier groups (“OCGs”) over a fiber link to another node in the network. The plurality of communication paths involve different signal and path attributes such as a plurality of carrier wavelengths, optical carrier groups, physical communication paths (different nodes, different fibers along a same path, or any combination of the foregoing), or any other differentiating factors between two paths.
In some embodiments of the present invention, skew compensation is accomplished on the transmission side of the network prior to transmission. The skew compensation can be based at least in part on determined skew relative to the communication paths.
In certain other embodiments of the invention, skew compensation can be accomplished at the receiver side. The receiver side can base skew compensation, at least in part, on the determined skew relative to the communication paths.
In some embodiments, skew compensation can be performed electronically. In other embodiments, skew compensation can be performed optically. Skew compensation can also be performed at an intermediary node on a path between the transmitting and receiving sides. In certain embodiments, skew compensation performed at the intermediary node can involve selecting certain communication paths between the intermediary node and the receiver node such that skew on the communication paths between the intermediary node and the receiver compensates for the skew between the transmitting node and the intermediary node.
Reference will be made to embodiments of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
The following description is set forth for purpose of explanation in order to provide an understanding of the invention. However, it is apparent that one skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of different computing systems and devices. The embodiments of the present invention may be present in hardware, software or firmware. Structures shown below in the diagram are illustrative of exemplary embodiments of the invention and are meant to avoid obscuring the invention. Furthermore, connections between components within the figures are not intended to be limited to direct connections. Rather, data between these components may be modified, re-formatted or otherwise changed by intermediary components.
Reference in the specification to “one embodiment”, “in one embodiment” or “an embodiment” etc. means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
The portion of the networking system shown in
In accordance with certain embodiments of the invention, nodes can be traditional analog nodes, digital nodes, hybrid nodes that allow signal management, or any combination thereof. Analog nodes may be amplifiers, or regeneration nodes. Nodes can also be digital nodes, implementing an optical to electrical to optical translation (“OEO”) such as described in case as disclosed and taught in U.S. patent application Ser. No. 10/267,331, filed Oct. 8, 2003, entitled “TRANSMITTER PHOTONIC INTEGRATED CIRCUITS (TXPIC) AND OPTICAL TRANSPORT NETWORKS EMPLOYING TxPICs” and in U.S. patent application Ser. No. 10/267,212, filed Oct. 8, 2002, entitled “DIGITAL OPTICAL NETWORK (‘DON’) ARCHITECTURE”, and U.S. Pat. No. 7,116,851, issued Oct. 3, 2006, entitled “AN OPTICAL SIGNAL RECEIVER PHOTONIC INTEGRATED CIRCUIT (RxPIC), AN ASSOCIATED OPTICAL SIGNAL TRANSMITTER PHOTONIC INTEGRATED CIRCUIT (TXPIC) AND AN OPTICAL TRANSPORT NETWORK UTILIZING THESE CIRCUITS”, all of which patent applications and patents are incorporated herein by reference. Reference to measuring signal performance can be implemented in either the electrical or optical domain.
Information can be transported as a signal or signals.
Each channel can be transported on a different communication path providing for added flexibility in routing the signals. Consequently, the networking system is not limited to selecting a path capable of transporting the entire signal since the signal is divided into multiple signal portions that can be transported separately. This improves QoS and permits higher bandwidth signal transportation over longer distances.
However, since the signal transported was divided prior to transmission, it must be combined at the receiving node 3220 to recreate the transported signal. In order for the original signal to be restored at the receiving node 3220, the skew between the channels 3260 and 3265 should be within a skew constraint. Skew may be defined as a variation relative to the initial timing of a component of a launched data signal or differential latency between the signal portions.
Skew can arise from many different causes depending upon the transmission medium and length over which information is communicated. For example, intrachannel skew and interchannel skew can arise because different wavelength carriers propagate at different rates. In particular, a high frequency carrier signal will generally take a relatively longer period of time to propagate along an identical length fiber as a lower frequency carrier signal. Skew can also arise because the different channels are transported on different paths. The paths may be of varying lengths or have varying numbers of intermediary nodes. Skew becomes an increasingly important consideration when routing signals on different paths because the skew can grow tremendously as a result of varying latencies between the paths.
One way to maintain skew at an acceptable level is by using skew compensation. Skew compensation can adjust the skew relative to at least two paths such that the skew is equalized. The skew adjustment can be implemented in many different ways. In one embodiment, the skew adjustment is accomplished using an electrical or an optical buffer. The buffer can be in the transmitting node 3210, the receiving node 3220 or any intermediary node, e.g. intermediary node 3270. In some embodiments skew compensation is accomplished using channel swapping. Channel swapping involves switching channels at intermediary node 3270 between transmitting node 3210 and receiving node 3220. The channel swapping can be based on the latency of each hop, for example the channel with the greatest latency on a first hop can be swapped with the channel with the least latency on a second hop.
As shown in
Embodiments of the present invention provide for route selection and skew adjustment 206A in communication network 206 via skew compensation module 260 in the control plane 220 of network 200. Skew adjustment is accomplished by skew compensation module 260.
There are a number of ways to compensate for skew or adjust skew, including, compensating for skew at the transmission node, at the receiver node, or at any or all intermediary nodes. Skew compensation can be achieved in the optical domain using one or more optical buffers, coils of fiber. Skew compensation can also be achieved in the electrical domain using one or more first-in-first-out (“FIFO”) buffers. The size of the optical and electrical buffers can be adjusted. Skew compensation can also be accomplished using latency balancing which can be implemented as channel swapping. Latency balancing can involve a determination of the latency of various hops or spans within the network and balancing the latencies among the spans or hops.
The modules and functionality shown in the control plane of
The present invention is well suited to any coupling arrangement, via any medium, to allow communication between the data and control planes in communication networks. The present invention may only link a portion of the nodes in parallel, which then could subsequently link a coupled series of nodes.
Alternatively, a distributed network management architecture could be employed. In particular, at least one node could have connectivity to another node (intranodal) to allow for the communication of resource status in the node for skew adjustment. The present invention is well suited to any form of connectivity that allows for distributed control for skew measurement, communication, status, control, and/or etc. to/from a node, e.g., by optical supervisory channel (“OSC”). A given gateway network element (“GNE”) might have connectivity to multiple service network elements (“SNEs”).
Alternatively, each node may have standalone skew measurement and correction capacities to simplify the required interaction between the nodes. The present invention is well suited to any combination of these or other control models that allow skew measurement and/or adjustment.
The quantity and frequency of channels within an OCG may vary in accordance with the network system and environment in which it operates. For example, an OCG may depend on the resources available on the network, the skew and traditional metric performances of the network, and a controller assigning the resources. The VSW1A is received and re-sequenced at the destination node (e.g. node N3) with acceptable skew performance, for reconstruction of the client signal and egress from the network. The information routing or skew adjustment described herein can be employed in combination or permutation with each other to provide additional options in routing and skew adjustment for the overall system.
The allocation of data across the multiple routes is determined by the skew between the channels (e.g., λ1, λK, λL, λM). If associated data signals are transmitted on route P1 410, then the resulting skew is the time difference between the earliest signal tE and latest signal tL occurring between the signals at their destination, node N3, illustrated as skew 404 (e.g., time ts1) with an associated skew dispersion slope of K1. Alternatively, if the associated data signals are transmitted via route P2 at 412, there results at the destination node N3 a timing skew 406 is illustrated, such as ts2, with an associated skew dispersion slope of K2.
The skew associated with the different routes P1 and P2 may be analyzed at the destination node to select an optimal route. These different skews may also be compared to certain parameters 408, such as max allowable skew tMAX, or maximum allowable skew slope KMAX. in order to select a preferred route. The skew may also be analyzed at intermediate nodes to select an optimal route or identify that skew falls within parameters.
The evaluation of skew may identify that skew has fallen outside of a preferred specification or range, and initiate a skew adjusting procedure. The skew consideration of each link, or span, in the network may be considered and summed for analysis relative to the allowable skew tolerance for a given communication network specification or standard.
The format of the signal portions may depend upon the protocol of a given system such as protocols defining the distribution of payload, forward error correction (“FEC”) data, overhead (OH) data, etc. Assuming initial timing 402 in
At an intermediate node, for example, if the signal is wavelength-swapped, then skew occurring between high and low frequencies can be compensated by inversing the wavelengths where the longest wavelength is swapped for the shortest transmission wavelength and the next longer wavelength is swapped for a shorter wavelength. In effect, the wavelengths are reversed in a manner that previously longer wavelength signals are substituted with shorter wavelength signals. For example, signal portion C3 and C2 are rerouted to be carried on swapped frequencies (e.g., C3 is now carried on λK and C2 is now carried on λL). This can be accomplished by optical signal wavelength conversion, or by an optical-to-electrical-to-optical conversion that reassigns a signal portion to be transmitted on a channel with a different frequency laser.
If associated data signals are received at node N2 with dispersion slope K3, as shown in the upper left side of
In an alternative embodiment, any signal portion can be reassigned to any carrier frequency, as best fits the overall skew reduction for the system, e.g., for non-linear channel performance as illustrated at 422 in
Referring now to
Referring now to
A VWG can be any size and grouping of signals as is appropriate for channel bandwidth between nodes, and that skew and other performance specifications allow. In the present example, associated data, VSW, is initially scheduled to be transmitted as associated client signal portions C1-C4 on carriers λ1, λK, λL, and λM, where client signal portions C1-C4 refer to a portion of the client signal that is transmitted on any available carrier, e.g., λ1, λK, λL, and λM. The specific content of C1-C4 and the specific wavelengths on any given path are decided by the controller, such as a central controller 302 or a node controller. Thus, as the traffic rate increases, the content distribution C1-C4 may vary across the respective carriers, e.g. λ1, λK, λL, and λM. In fact, if the controller so evaluates it, the client signal may be adjusted from content distribution C1-C4 on carriers, e.g., λ1, λK, λL, and λM to content distribution C1-C3 on respective carriers, e.g. λ1, λK, λL, and λM.
However, in this illustration, sufficient channel count, or bandwidth, was not available on path P3 470 between the source node N1 and the destination node N3 to co-route the entire client signal (e.g., client signal portions C1-C4) as a Virtual Super Wavelength, VSW1B 464. Consequently, the exemplary controller, evaluate the network demands (e.g., traffic load, network resources, bandwidths, etc.) and conclude that the VSW should be divided into two or more virtual wavelength groups. For example, VWG1 may be divided into client signal portions C1 and C4 on carriers λ2 and λ31 on transmitted on path P3 470, and wavelength group VWG2 may be divided into client signal portions C2 and C3 on carriers λ4 and λ5 on path P4 472. For simplicity, it is assumed that carrier wavelengths are consistent across the several spans shown, though carrier wavelength diversity can be used.
Note that in the present embodiment, client signal portions C1 and C4 are co-routed as one VWG2 on outer wavelengths λ2 and λ31, while client signal portions C1 and C4 are co-routed as another VWG3 on nominal wavelengths λ4 and λ5, similar to that illustrated in prior
Different quality of service signals may be routed in this manner to provide preferred performance characteristics. If client signal portions C2 and C3 are more time-sensitive, or contain more sensitive data, the portions may be transmitted on a preferred physical route, preferred carrier wavelength, preferred grouping, and/or preferred fiber (i.e., preferred with respect to minimized skew slope, signal dispersion, fiber dispersion, and resultant skew between client signal portions).
A client signal portion by itself, or a VWG, may be re-routed at a node to travel a different path. A re-routing of this sort is accomplished by communicating the client signal portion(s) to a multiplexing device, such as a band multiplexing module (“BMM”) shown in subsequent
Referring in particular to
Transceiver node 502 is a multi-channel device with multiple DLM 503 modules each of which contain an RxPIC and a TxPIC, a group of which are coupled into a band MUX module (“BMM”) that multiplexes the range of wavelengths (e.g., TxPIC1 λ1 through TxPIC8 λ32) into a WDM signal for transmission on fiber link 510 to a downstream node. Inputs 508 and 509 are coupled from upstream nodes in the communication network. Within each DLM, electronic processing and switching blocks 522 and 523 provide options to manage the transmitted information in the electrical digital domain, including skew management functions, described in more detail in subsequent figures. While all the wavelengths processed by transceiver 502 may be within in the C-band, this band may be divided between a red portion of the C-band, to represent lower wavelengths in the signal spectrum, and the blue portion of the C-band, to represent higher wavelengths in the signal spectrum. While the present embodiment constrains the spectrum of wavelengths for transmission within the C-band, the present invention is well-suited to using any combination and location of wavelengths such as utilizing multiple bands, e.g., L-band, S-band, any other band or to utilizing divisions within a band, for communication path diversity.
In certain embodiments, two nodes may be coupled via multiple fibers that can be selected for their different skew properties, such as their different dispersion properties between channels that will allow carriers at different wavelengths to arrive at a downstream node at different times. Transceiver node 502 has BMM2 521 coupled to node N3 via switch 526A and 526B on either end of the multiple links 512 through 516, which correlate, for example, to fiber F1 440 through fiber FN 444 of
Referring now to
Referring specifically to
Certain embodiments provide coupling from the photodetectors to a programmable skew measurement device 622. The skew measurement device is enabled to capture skew measurements via a comparator (e.g., a differential sense amplifier, and other digital signal processing techniques) that correlates the output from a photodetector with a predetermined bit pattern. The bit pattern is replicated in a marker of a test signal transmitted to the DLM 503A during a learning mode for the network. Skew measurement device 622 has multiple instances of correlation ability along with a local clock input for measuring the difference in time from receipt of the marker for each of the multiple channels λ1 to λN. Alternatively, programmable skew measurement device 622 may include the capability to perform a relative comparison measurement between any two wavelengths at a given time for comparison testing. This pattern can be repeated for different wavelengths, as directed by local controller 620, in combination with a central network controller.
Local controller 620 is coupled to skew measurement device 622, in the control plane 632, to provide initiation signals for test mode, selection of wavelengths to measure, and reception of skew data. Local controller 620 in the current node is coupled via a unidirectional or bidirectional line 624 to other nodes in the network to share skew data measurements, skew resource status, skew needs, and skew resource allocation.
Besides providing skew measurement control, various nodes in these embodiments of the invention provide an optional skew compensator 608 for each channel in the optical domain 602 of the node and optional skew compensator 610 in the electrical domain 604. Skew buffer 608 may be any optical device with delay properties, such as a ring resonator. In various embodiments, an optional skew compensator is provided for only a portion of the signal channels in the DLM 503A, such as on channels on which signals propagate at a higher rate per unit time, such as those on lower frequency channels. In other embodiments, optional skew compensator has a bypass that is enabled via local controller 620 if no skew adjustment is needed. Lastly, in another embodiment, no optical skew compensation is used because of higher cost, and sufficient capability of skew adjustment via routing, and/or buffering in the electrical domain.
Similar to optical skew buffer 608, an optional electronic skew compensator 610 may be any buffer medium, such as a first-in-first-out (“FIFO”) memory buffer, which delays the information on the given channel. In different embodiments, the optional electronic skew compensator 610 can be implemented on all channels, or only on a fraction of the channels. The optional optical skew compensator 608 can be programmable to allow a variable amount of delay on the information transmitted thereon, with a bypass to reduce any incidental propagation delay that the device may exhibit even if no skew compensation is desired. Additionally, the optional electronic skew compensator 610 may be located anywhere within the optical networking system, including at transmitting nodes, receiving nodes and intermediary nodes. After the appropriate buffering in the receiver, the electrical signals are communicated to switch 612, which can be any form of switch, such as cross-point switch, which enables rerouting of information signals from one channel, or wavelength, to another channel, or wavelength.
Referring specifically to
Increased bandwidth that can be gained from co-routing signal portions as described can be particularly advantageous in submarine optical systems, for example, in communicating between continents where the communication spans large bodies of water.
On the transmission side of the system, a plurality of channels 2105 is optically multiplexed, via multiplexer 2110, to generate a WDM signal. The WDM signal is communicated along the optical span having multiple optical amplifiers or regenerators 2115 that keep the WDM signal power within a preferred range. A coarse dispersion compensation module 2120 is coupled to receive the WDM signal after having traversed all or substantially all of the optical span. The coarse dispersion compensation module 2120 compensates for dispersion effects on the WDM signal along the span, which causes signal degradation. In various embodiments of the invention, the coarse dispersion compensation module 2120 comprises dispersion compensating fiber or fibers that reduce the dispersive characteristics of the WDM signal. As the WDM travels through these dispersion compensating fiber(s), the shape of the signal is improved resulting in a better signal-to-noise ratio.
One skilled in the art will recognize that various compensating systems may be realized with different types and combinations of dispersion compensating fibers. Because the coarse dispersion compensation module 2120 compensates for dispersion across the channels of the WDM signal (i.e., the WDM signal is multiplexed), targeting certain channels within the WDM signal for dispersion compensation is difficult. Accordingly, certain embodiments of the invention provide for additional fine dispersion compensation at a channel granularity.
An optical demultiplexer 2125 separates the WDM signal into individual channels, optical signal groups, or a combination thereof. A plurality of fine dispersion compensation modules 2130 receive optical channels or optical signal groups and further apply dispersion compensation thereon. In certain embodiments of the invention, each fine dispersion compensation module 2130 is designed to compensate a certain channel or group of channels. Dispersion compensation fiber may be used within the plurality of fine dispersion compensation modules 2130.
The coarse dispersion compensation module 2120 and the fine dispersion compensation module 2130 introduce additional latency within the WDM signal. These latency effects become even more detrimental when the added latency is not spread evenly across each of the channels. In such situations, this uneven addition of latency further increases the amount of skew between one or more of the channels resulting in a more complex and demanding reassembly procedure if not address prior thereto.
Each of the dispersion compensated channels is converted into the electrical domain by a plurality of optical-to-electrical converters 2135. These converters 2135 may include PIN diodes, photoavalanche diodes, or other converters known to one of skill the art. The resulting electrical signals are provided to a plurality of skew compensating modules 2140 that adjust the differential latency between the channels so that a signal, transmitted across at least two of the channels, may be more efficiently rebuilt. This skew compensation may be achieved by effectively introducing additional latency within one or more of the channels by performing a post-buffering operation thereon. One skilled in the art will recognize that the buffer size in each of the skew compensating modules 2140 may be adjusted to enable compensation of more or less skew.
As previously discussed, skew is potentially introduced into a client signal as the channels within the WDM signal travel across the optical span and are processed within dispersion compensation modules (e.g., 2120, 2130). This skew may be compensated on the transmission side of the optical signal by pre-buffering one or more of the channels within the WDM signal, by buffering one or more of the channels within the WDM signal at an intermediary node, or post-buffering one or more of the channels at the skew compensating modules 2140, or any combination thereof. According to various embodiments of the invention, the skew compensating modules 2140 may also provide skew analysis functionality in which skew across the channels is monitored. If the skew falls outside of a desired range, a skew compensating module 2140 may generate an alarm and/or dynamically re-allocate the channels to improve the skew. Furthermore, as detailed in
Although skew compensation has been described as being performed in the electrical domain, one skilled in the art will recognize that skew compensation may also be done in the optical domain. For example, additional latency may be added to one or more channels by using an optical buffer, such as a fiber coil, to add this latency.
In various embodiments of the invention, the electrical channels are provided to a plurality of coarse skew compensating modules 2205. These modules 2205 provide a coarse adjustment of differential latency between at least two of the electrical channels. This reduction of differential latency may be achieved by buffering one or more of the electrical channels for a set period of time, which effectively reduces the corresponding skew or differential latency between the electrical channels. A plurality of fine skew compensating modules 2210 further refines the skew compensation across certain channels. In certain embodiments of the invention, the plurality of fine skew compensating modules 2210 analyze certain skew characteristics remaining after the coarse skew adjustment and further adjust the channels to further improve the corresponding skew. One skilled in the art will recognize that either or both of the coarse skew compensating modules 2210 and the fine skew compensating modules 2215 may be integrated with other electrical components within the node. For example, the fine skew compensating modules 2215 may be integrated within an electrical multiplexer 2215 that combines one or more electrical channels into a client signal.
Further electrical components or modules may be provided within the signal paths that analyze, modify or otherwise process these compensated electrical channels. These electrical components may or may not be located between the coarse skew compensating modules 2210 and the fine skew compensating modules 2215.
Using the compensated electrical signals, a client signal 2220 is transmitted from the electrical multiplexer 2215 and is generated by combining one or more of the electrical signals into a relatively higher data rate signal. This combination of electrical signals is less demanding if there is little or no skew between its component electrical channels.
In various embodiments of the invention, pre-skew compensation is performed exclusively on the transmitting node 2305, which compensates for skew across the first terrestrial network 2310, the submarine optical system 2320, and the second terrestrial network 2330. These embodiments may be more typical if a service provider is using a third-party submarine optical system to inter-connect terrestrial networks and does not have control of the landing nodes of the submarine optical system.
In other embodiments, skew compensation may be diversified throughout the system in which the first and/or second landing nodes 2315, 2325 further comprise skew compensation modules. Such a diversification allows a relatively lower amount of pre-compensation to be performed on the transmitting node 2305 and a relatively lower amount of post-compensation to be performed on the receiver node 2335. Additionally, this diversification may also provide early fault or error detection if skew becomes too large at some point within the system.
One skilled in the art will recognize that the above-described method for calculating latency across diverse paths may be applied to any number of paths greater than two. Additionally, the method may be applied to any type of network including, but not limited to, submarine, trans-oceanic optical systems.
The flowchart in
While the invention has been described in conjunction with several specific embodiments, it is evident to those skilled in the art that many further alternatives, modifications and variations will be apparent in light of the foregoing description. Thus, the invention described herein is intended to embrace all such alternatives, modifications, applications, combinations, permutations, and variations as may fall within the spirit and scope of the appended claims.